Power toothbrush and guard therefor



May 19, 1970 111.. TAYLOR 3,512,202

POWER TOOTHBRUSH AND GUARD THEREFOR Filed May 31, 1968 v H6 ,1 FIG.7 I2 150 INVENTOR. THEODORE L. TAYLOR FIG. I a,

ATTORNEY United States Patent 3,512,202 POWER TOOTHIERUSH AND GUARD THEREFOR Theodore L. Taylor, 4813 Woodburn Drive, Madison, Wis. 53711 Continuation-impart of application Ser. No. 633,556, Apr. 25, 1967. This application May 31, 1968, Ser. No. 733.436

Int. Cl. A61c 17/00; A46b 13/02 US. CI. 15-23 11 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation-in-part of application Ser. No. 633,556, filed Apr. 25, 1967, entitled Power Toothbrush.

This invention relates to power toothbrushes, more particularly the rotary brush head type. In its preferred form this invention employs dual brush heads.

Various motions have heretofore been proposed and used in power toothbrushes. The principal motions are: reciprocating, oscillating, rotating. However, no single motion alone is entirely satisfactory for the complete toothbrushing operation.

Reciprocation of bristle tips transversely of tooth faces and gingiva is generally undesirable, because continuous straight line motion of the tips across teeth and tissue may be severely injurious thereto. Such action may injure the tooth enamel, even cut grooves therein. Gingivitis may develop, and in any event, not only is brushing across the gingiva hazardous, such action does not effectively clean under the gingiva, in the crevices, or provide proper ton- The most effective brush motion for general cleaning along the fronts and backs of the teeth is a rotary sweeping motion, beginning just above the gum line and continuing along the tooth face to the biting edge. A similar rotary or rocking motion is generally effective for cleaning the tops of molars and bicuspids. In the case of power toothbrushes, efforts have been made to simulate the desired action of the bristles by a rapid oscillatory motion of the brush head, with the intent that the user hold the brush with its head shaft parallel to the gum line, the brush tips then sweeping back and forth across the faces of the teeth. However, this scheme has the serious disadvantage that for half of each cycle the bristle tips move in the wrong direction, that is, toward the gingiva, in large part nullifying the effectiveness of the brushing action in the other half cycle, the result being largely moving debris back and forth along the teeth rather than removing it. Furthermore, when brushing near or upon the gingiva, as is necessary for removal of debris from beneath them and for toning, the reverse motion of the bristle tips may cause serious damage. Due to the relatively high speed at which a powered oscillating brush head operates, it is impossible to offset or ameliorate the undesirable bristle action by manipulation.

Because of the foregoing objections to reciprocating and oscillating bristle motion, a steady rotary brush head motion is preferable for cleaning tooth surfaces under power operation, with the bristle tips steadily sweeping unidirectionally in an arcuate path. By providing a reversible drive, the direction of rotation can be established as required for brushing up or down, or from right or left hand, as required for cleaning in the various areas. However, I find that for cleaning between teeth, even the rotary motion may often be largely ineffective, due to the tendency merely to force debris into the crevices under pressure of the bristles, and without dislodging particles adhering tightly to tooth faces. These objections can be avoided or minimized by vibrating the bristles, with the bristle tips held stationary for a short period, the vibration loosening the particles sufliciently, so that, upon resumption of the arcuate sweep, the particles will be removed, rather than pressed onto the teeth and into the crevices.

It is desirable that a brush guard be provided, to obviate the rapidly rotating brush bristles scraping and damaging the delicate tissues of lips and cheeks inside the oral cavity. With a reversible brush, the guard must also be reversible, to provide effective shielding in alternative positions of the brush corresponding to the alternative brush rotation. Such guard reversal is preferably automatic, to eliminate the risk that user may otherwise apply the brush with the same rotating in the wrong direction for desired brushing position.

It is a principal object of this invention to provide in a power toothbrush a dual head motion, whereby most effectively to clean all surfaces of the teeth and gums, as well as crevices, throughout the mouth, with a minimum demand or reliance on manipulation by the user.

Another object of this invention is to provide in a power toothbrush having a reversible brush an automatically positioned reversible guard, whereby the guard is at all times in proper shielding position corresponding to correct brush rotation for selected brushing position.

Yet another object of this invention is to provide a power toothbrush which is convenient to use and yet effects satisfactory, dependable tooth cleaning and gum massage with a minimum demand for manipulation by the user.

The foregoing and other objects and advantages of the invention will be apparent upon reading the following description in conjunction with the accompanying drawings, wherein:

FIG. 1 is a foreshortened side view of the toothbrush of this invention, with a portion of the case cut away to expose the drive and control mechanisms therein;

FIG. 2 is a head end view of the brush assembly taken on line 22 of FIG. 1;

FIG. 3 is a transverse section through the case on line 3-3 of FIG. 1;

FIG. 4 is a transverse section taken through the reciprocating drive plate on line 44 of FIG. 1;

FIG. 5 is an enlarged section on line 55 of FIG. 4, showing details of connection between reciprocating shafts and the reciprocating plate;

FIG. 6 is a circuit diagram showing the electrical system and apparatus for driving and controlling the brush heads; and

FIG. 7 is a view showing a modified gear train for driving dual brush heads in the same direction of rotation; and

FIG. 8 is a section on line -88 of FIG. 1.

Referring now to FIG. 1, reference numeral 10 indicates the case for the drive and control elements, which case also serves as a handle. Case 10 is provided with removable caps 11 and 12, which seal the case and permit access for insertion and removal of the drive and control components. The caps may be fastened to the case in any suitable manner, for example, by means of dowels or screws (not shown).

A gearmotor 14 is set into case approximately mid way thereof, with an extended coaxial output shaft 15 projecting toward cap 11. At its outer end shaft 15 carries a wide-faced spur gear 16. In order to minimize bending load and whip of shaft 15, and for another purpose later to be described, a support plate 17 is provided about midway of the shaft extension, having a close-fitting central aperture 18, through which the shaft 15 extends.

Gearmotors such as that here illustrated are wellknown and commercially available. Therefore, detailed description thereof is not necessary here. Gearmotor 14 is selected for an output shaft speed which is best suited to producing the desired brush head speed through an associated drive train which meets the space limitations and efliciency requirements for the particular combination. In the embodiment here illustrated gearmotor shaft speed of 500 r.p.m. is desirable, involving a 7/ 1 reduction unit in gearmotor 14 from synchronous full load motor speed on 60-cycle-AC power supply. Gearmotor units having other output speed and/or reduction ratios are available or readily made in accordance with well known practices, as may be required for other power supply drive trains and ultimate brush-head speed.

The example here illustrated involves driving twin rotary brush heads 19 and 20 through twin drive shafts 21 and 22, which at their inner ends are journalled in support plate 17 parallel to and alongside gearmotor shaft 15. Shafts 21 and 22 carry spur gears 23 and 24 in mesh, gear 24 in turn meshing with gear 16 on output shaft 15. A solenoid 25 is mounted on motor face plate 26 alongside output shaft 15, with the reciprocating solenoid output shaft 27 midway between drive shafts 21 and 22, shaft 27 extending through support plate 17.

As best seen in FIG. 2, brush heads 19 and 20 are of the same outside diameter. For uniform cleaning action both brush heads preferably rotate at the same speed. Therefore, the gears 23 and 24 are preferably meshed in 1/1 ratio, as best seen in FIG. 3. As will be apparent from inspection of FIG. 1, the diameter of gears 23 and 24 is a function of the diameters of brush heads 19 and 20, which in turn are primarily determined by considerations of dental structure and accessibility in the oral cavity, together with the requirement of providing a brush drive and case which are as simple, safe and convenient as possible. In the arrangement illustrated here it is found that gear 16 need be somewhat larger in diameter than gears 23 and 24, whereby brushes 19 and 20 rotate at a speed somewhat greater than that of gearmotor drive shaft 15. For example, with 500 r.p.m. for shaft 15, brushes 19 and 20 rotate at 1000 r.p.m. With brush heads approximately A inch in outside diameter, which I have found to be a suitable size, the bristle tip speed is about 13 i.p.s., substantially an optimum cleaning speed from the standpoints of safety and effectiveness.

Referring again to FIG. 1 and also to FIG. 4, an elliptical bridge piece 28 spans drive shafts 21 and 22, apertures 29 and 30 being slightly larger than the diameter of shafts 21 and 22, so that the latter may rotate freely with respect to bridge 28 when driven by gear motor 14. Solenoid shaft 27 extends through aperture 31 in bridge 28. Ferrules or washers 32 are affixed to shafts 21, 22 and 27 in position to constitute flanges on both sides of the bridge 28 along each of the shafts. Thus, when solenoid 25 is energized, brush shafts 21 and 22 will reciprocate with solenoid plunger 27, gears 23 and 24 remaining in mesh and gear 24 remaining in mesh with gear 16, the latters face being somewhat wider than that of gear 24 to insure full engagement in any axial position of the lat ter within the stroke range, and with allowance for normal variations in assembly.

Operation of the gearmotor 14 and solenoid 25 is controlled by means of (1) a manual switch 33, conveniently located in the wall of case 10 at a position readily accessible to the users thumb when gripping the case for comfortable manipulation of the brush assembly, (2) a timer 34, with rotary contactor 35, in the rear of case 10, behind gearmotor 14, and (3) interlocking electric circuitry, best seen in the block wiring diagram in FIG. 6. Terminals T and T indicate the prongs of the conventional electrical plug in circuit through an external switch 33, such as a toggle switch, serving as a safety switch, permitting the brush to be left plugged in, but guarding against accidentally energizing the brush mechanism while handling the unit when not in actual use. Closing of the switch 33 at T connects T to timer 34 at T and to one leg of contactor 35 at T T on the other leg of contactor 35 is connected to solenoid 25 at T The other leg of contactor 35 is connected from T to T on one throw of switch 13 and to T on the other throw of switch 13.

Input terminal T is directly connected to T of timer 34, T of solenoid 25, T on one throw of switch 13 and T on the other throw of switch 13.

Throw-arm double-contactor 37 of switch 13 is directly connected through T and T to terminals T and T respectively of gearmotor 14.

T and T are on a winding of gearmotor 14 for operation in one direction of rotation, while T 9 and T are on a winding of gearmotor 14 for operation in the opposite direction of rotation. Therefore, throwing switch arm 37 in one direction establishes a winding circuit for forward motor operation and throwing the arm in the other direction establishes a winding circuit for reverse rotation. However, as previously noted, one switch pole on each motor winding circuit is connected through rotary contactor 35 on shaft 38 of timer 34. Contactor 35 is of the rotary, wiping-cam type, wellknownin the timer art, thus not requiring description here in detail. The wiper cam 39 is in this case selected to establish circuit between T and T during a portion of a revolution. The arc of contact is selected to establish the relative port-ions of the revolution in each circuit contact, while the speed of the timer 34 determines the period of contact in each circuit, contact to T energizing gearmotor 14 and contact to T energizing solenoid 25, while cutting off gearmotor 14.

When solenoid 25 is energized, brush heads 19 and 20 reciprocate by virtue of the arrangement previously described. The stroke of solenoid plunger 27 is preferably quite short, on the order of A to as determined by the selection of solenoid Winding and armature according to well-known principles. With the user holding the brush bristles firmly against the teeth in the normal rotary cleaning operation of the heads 19 and 20', the introduction of reciprocating motion, While cutting off the rotary motion, will cause the bristles to vibrate in the direction of the solenoid plunger stroke, the stroke being so short that the tips of the bristles do not move, pressure against the teeth precluding tip motion. This action may aptly be termed vibrato. I find that this vibrato action is extremely effective in loosening particles of debris, particularly in the crevices, whereafter resumption of rotary head motion sweeps the debris from the teeth and out of the crevices. Assuming a total brushing time of 30 seconds in a given region without substantial translation of the brush heads, about 7-8 seconds is a desirable portion of the total brushing time in one region for vibrato action. Therefore, timer 34, of the usual geared type, is selected for a shaft speed of 2 r.p.m., with motor contact during of each revolution and solenoid contact during the other 25% of each revolution. However, it will be obvious that the timer and contactor can be selected in various combinations for other time cycles, such timers and contactors being available in a Wide variety of combinations.

Referring again to FIG. 1, the extended portions of shafts 21 and 22, beyond cap 11, are journalled in sleeve 40, which is generally elliptical in cross-section, as best seen in FIG. 2, baffles 41, 42 supporting the shaft extensions to minimize whip and undesirable lateral vibration. An inner end portion of housing 40 extends through aperture 43 in cap 11, hearing on wall 44 of aperture 45 in bushing 46, while the inner end portion of baffie 42 extends through aperture 43 and bears on wall 47 thereof, anchoring the shaft housing assembly against accidental dislodgement or shift. It will be understood that brush heads 19 and 20 may be splined or otherwise removably coupled to shafts 21 and 22, to facilitate replacement of worn brushes, or interchange for hygienic reasons, if the unit is to be used by several persons. Means for such removable brush attachment are well known in the art and therefore not here illustrated or described in detail.

A lip and cheek guard 48 is preferably provided adjacent brush heads 19 and 20*, so that the bristles thereof will not inadvertently scrape soft oral tissues. Guard 48 is preferably made of relatively rigidmaterial, to serve its protective function, yet conform comfortably in the oral cavity in various brushing positions, and is arranged to provide for reversal of brush exposure when cleaning on opposite sides of the teeth, or changing hand, according to the direction of brush rotation, as hereinafter described.

The gear drive above described is adapted to rotate the brush heads in opposite directions. This arrangement is slightly disadvantageous for brushing behind the teeth, since, with the opening necessary for the holder, the heads must be moved up and down to reach uppers and lowers, only one brush being operative at a given instant. If desired, the brushes can be geared for rotation in the same direction by use of an idler gear, as shown in FIG. 7, wherein parts corresponding to those of previous drawings are correspondingly numbered, with the addition of 100. Drive gears 123 and 124 are here separated, gear 124 being meshed with gear 116, on gearmotor shaft 115. Idler gear 150 is interposed in mesh with gears 123 and 124, on brush head shafts 121 and 122, so that the latter rotate in the same direction, as indicated by the arrows. The idler gear shaft 151 may bemounted on plate 17 (FIG. 1), just below bridge piece 28. With the brush heads rotating in the same direction, both brushes are applied to the same line of teeth at one time, one operating on or near the gingiva, the other toward the tooth edges. In such case one brush in effect feeds debris to the other, providing a conveyor action.

With either brush drive arrangement, the reversing switch 13, indicated diagrammatically in FIG. 6, may be conveniently incorporated into the cap 11,;in the form of a rotary switch having contactors forforward, oif and reverse motor conditions, as previously described. A suitable location of switch 13, in the arrangement shown in FIG. 1, is between cap 11 and case 10, as indicated gen-' erally by the reference numeral 13. Switch structures of this type are well-known in the electrical appliance arts, as used on mixers, blenders, fans and other multi-speed appliances. In this instance, suitable indicia may be provided on the cap 11 and adjacent portion of case 10. The user can readily position the cap and switch 13 for selected motor condition by turning the cap with thumb and index finger, while holding case with the palm or the other hand. However, other switch arrangements may be used.

Referring again to FIGS. land 2, guard 48, comprising arcuate WingS 49 and 50, is afiixed to the outer end of shaft 47, which extends axially of sleeve 40 from the inner end fixed in cap 11 at the center thereof. As best seen in FIG. 8, shaft 47 is free to rotate relative to sleeve 40. Therefore, as cover switch-plate 11 rotates along contacts of switch 13, guard wings 49 and 50, joining at shaft 47, rotate with plate 11 through the same angle of rotation. As best seen in FIG. 2, about 90 rotation of shaft 47 fully reverses guard 48, bringing wing 49 from shielding position at one extreme, represented by the full lines, to the position represented by broken lines, at which latter position wing 50 shields brushes 19, 20 from the side opposite to that of wing 49. The opening 43 in the face of cap 11 is a sector of about angle, as defined by edges 51, 52, so that the cap is free to turn the amount required to reverse guard 48. The contacts in switch 13 are spaced 90, positioned and connected to the motor in such manner that with contact at given terminal the motor rotates the brushes in the direction corresponding to the guard position established by turning cover 11 to such given contact.

When one guard wing is in shielding position, the other wing, by virtue of its retraction and relatively stiff material, is maintained in such attitude relative to the users oral cavity as may be comfortable at selected brushing position.

It will be apparent from the foregoing description that the power toothbrush of this invention is highly advantageous in providing for effective tooth cleaning with minimum manipulation by the user, by virtue of programming dual brush action for the stages of loosening and removing debris from the teeth and gingiva, safely and fully. While I have illustrated and described a preferred embodiment of the invention, it will be understood that those skilled in the art Will thereby be enabled to devise variations and modifications without departing from the spirit and scope of the invention, as defined in the appended claims.

The invention may be embodied in a unit having a single brush, should a more compact and less expensive appliance be desired. In such case, the housing, caps, drive parts, shaft sleeve may be simplified or reduced in size, as appropriate to the reduced mechanical and space requirements, although the general construction and mode of operation remain in principal aspects as heretofore described.

I claim and desire to secure by Letters Patent the following:

1. A power toothbrush comprising: a rotary brush; a shaft carrying said brush; reversible drive means connected to said brush; switch means associated with a portion of said drive means for selectively establishing the direction of rotation of said brush; a reversible guard for said brush, said guard having a first shielding position relative to one portion of said brush, corresponding to one direction of brush rotation, and having a second shielding position relative to a second portion of said brush, corresponding to the other direction of brush rotation; means shiftably supporting said guard independently of said shaft; and means associating said guard with said switch means for shifting said guard to said first position as said switch means establishes said one direction of brush rotation and shifting said guard to said second position as said switch means establishes said other direction of brush rotation.

2. A power toothbrush according to claim 1, further including a second rotary brush adjacent to said firstnamed brush, said second brush being connected to said drive means, said brushes being rotatable on substantially parallel axes, said guard shielding both said brushes simultaneously when said guard is in either of said positions.

3. A power toothbrush according to claim 2, .wherein said guard comprises first and second wings, said first wing shielding said brushes when said guard is in said first position, said second Wing shielding said brushes when said guard is in said second position.

4. A power toothbrush according to claim 2, wherein said switch and guard shift associating means includes a rotatable shaft substantially parallel to said brush shafts, said guard being affixed to said shifting shaft.

5. A power toothbrush according to claim 4, wherein said guard comprises a pair of wings affixed to a hub therebetween, said guard being affixed to said shifting shaft at said hub.

6. A power toothbrush comprising: a handle; a reversible motor in said handle; a brush shaft driven by said motor, said brush shaft extending from said handle; a rotary brush on said brush shaft outwardly of said handle; a switch carried by said handle, said switch being adapted for selectively conditioning said motor to drive said brush shaft in either direction of rotation; a guard shaft connected to said switch, said guard shaft being substantially parallel to said brush shaft; a guard carried by said guard shaft outwardly of said housing in position to shield said brush, said guard comprising a pair of wings aflixed to a hub therebetween, said hub being afiixed to said guard shaft, said wings and hub being so configured that when a first one of said wings is in shielding position relative to a first portion of said brush, the second one of said wings is in a retracted position, exposing a second portion of said brush; and said guard shaft being so connected to said switch that when said switch is in a first position conditioning said motor to drive said brush in one direction, said first wing shields said first brush portion, and when said switch is in a second position conditioning said motor to drive said brush in the other direction, said second wing shields said second brush portion.

7. A power toothbrush according to claim 6, further including a second rotary brush on a second brush shaft adjacent and parallel to said first-named brush shaft, said second brush shaft being driven by said motor simultaneously with said first brush shaft, said guard being adapted simultaneously to shield both said brushes.

8. A power toothbrush according to claim 7, wherein said brushes rotate in the same direction when said motor runs in a given direction.

9. A power toothbrush according to claim 7, wherein said brushes rotate in opposite directions when said motor runs in a given direction.

10. In a power toothbrush having a pair of closely spaced brushes rotatable on parallel axes and a guard shaft pivotable on an axis parallel to said brush axes, all said axes being substantially in a common plane, with said guard shaft laterally of said brush pair, a brush guard comprising a pair of wings aflixed to a hub, said wings projecting generally in opposite directions from said hub, said hub being afixed to said guard shaft, each said wing being of a shape and size suitable for hooding said brush pair at a side thereof when said guard shaft is in a predetermined pivot position.

11. In a power toothbrush, a guard according to claim 10, wherein said wings and said hub are so configured relative to said brushes that with said guard shaft in a first rotary position, a first wing extends generally parallel to said plane in a shield position along one side of said brush pair, the other side of said brush pair being exposed for brushing action, and, with said guard shaft in a second rotary position the second of said wings is in shield position along the other side of said brash pair, said one side being exposed for brushing action.

References Cited UNITED STATES PATENTS 2,279,982 4/1942 Glynn 1523 3,161,899 12/1964 Poizat .15-23 EDWARD L. ROBERTS, Primary Examiner 

